The invention is based on a cooling fan, in particular for vehicles.
In a known cooling fan of this type, also called a ventilator or blower, (DE 43 29 804 A1), the fan wheel is pressed against the motor shaft and, in order to fasten the motor to a component in the vehicle, a mount is provided which secures the electric motor on its stator which constitutes the pole housing. The mount is manufactured in two parts comprising a motor mount and an adapter, and a number of rubber-elastic support elements are disposed between the motor mount and adapter, which vibrationally decouple the unit made up of the electric motor and the fan wheel and consequently damp a noise transmission to the vehicle parts.
In electric motors of the external rotor type (DE 196 52 263.3), in order to reduce the structurally induced intense noise generation of an external rotor, the proposal has already been made to produce the bell-, cap-, or cup-shaped pole housing encompassing the stator out of a three-layer composite sheet metal in which a plastic layer is embedded between two covering layers of iron or steel.
The cooling fan according to the invention, has an advantage that due to the use of an electric motor of the external rotor type, it is embodied in a very compact, space-saving manner and the motor, it has a low noise level that is sufficient for cooling fan purposes so that an expensive manufacture of the pole housing of the electric motor out of composite sheet metal can be eliminated. This is achieved according to the invention because, the fan wheel rests against the circumference of the pole housing and therefore prevents the housing from vibrating. As a result, body sound waves, which are produced by changing forces and moments acting on the pole housing, are strongly damped and can only be transmitted in a sharply reduced form via the outer surface of the pole housing. This damping action is actually not as good as when a composite sheet metal is used for the pole housing, but it is completely sufficient for cooling fan purposes since the remaining noise still being transmitted by the rotor falls below the noise level of the fan wheel. Among other things, the quality of the damping depends largely on the forces with which the fan wheel presses against the pole housing at the contact points and also depends on the damping action of the fan wheel itself, which constitutes a spring-damper system. The damping action of the cooling fan is influenced by the geometric design and by the choice of material.
Advantageous improvements and updates of the cooling fan are possible measures set forth hereinafter.
According to a preferable embodiment form of the invention, the contact points of the fan wheel are located at the points of the pole housing in which the greatest vibrational amplitudes occur in the pole housing. Since the bell-, cap-, or cup-shaped pole housing exhibits the greatest vibrational amplitude at the leading edge, similar to a bell, according to a preferred embodiment of the invention, the contact points of the fan wheel are intentionally placed in this vicinity and are preferably embodied by damping projections which protrude inward radially from the end face of the fan wheel disposed in the vicinity of the bell edge of the pole housing and are of one piece with this end face.
This is achieved in a structurally simple manner according to an advantageous embodiment of the invention, the fan wheel is provided with a cylindrical wheel part which axially encompasses the pole housing at least partially with a radial gap and is supported against the pole housing by the above-mentioned damping projections, which are preferably disposed evenly distributed over the circumference, wherein in order to improve the damping action, axial slots are formed into the cylindrical wheel part of the fan wheel, preferably distributed evenly over the circumference.
Alternatively or in addition, according to an advantageous embodiment of the invention, additional damping shaped parts are disposed between the fan wheel and the pole housing. In the embodiment of the fan wheel with a cylindrical wheel part, with a shaped part embodied as a ring, this shaped part is contained in a diametrically enlarged end section of the pole housing, wherein the shaped part is supported against the inner wall of the end section and against the outer circumference of the pole housing.